There are major problems in interrupting currents having a large DC component or a delayed zero crossing, as can happen on the appearance of certain types of faults, e.g. in high tension AC networks with series compensation. The presence of the DC component can prevent the current from passing through zero for several pseudo-periods. That makes it impossible to interrupt the current using conventional sulfur hexafluoride circuit breakers.
To remedy such problems, it is well known to increase arc tension by suitable means. High arc tension makes it possible to absorb the energy of the DC component and cause it to tend to zero.
For this purpose, French patent document No. 2 681 724 proposes using an interrupting chamber provided with means for creating a plurality of arcs in series.
Proposals have also been made in French patent document No. 2 678 770 to use an interrupting chamber having permanent fuses in series with a conventional high tension interrupting chamber. The melting of the fuses when tripping on a fault produces a very high arc tension which causes the DC component of the fault current to decrease very rapidly.
It is also known that the energy of the network due to the DC component can be absorbed by temporarily inserting a resistance in the circuit. A suitable resistance makes it possible to cause the DC component to tend towards zero in a relatively short time. One such disposition is described in French patent document No. 2 683 937.
It is also known that having a large-capacitance capacitor in series with an inductor disposed in parallel with an interrupting chamber of a circuit breaker gives rise to current oscillations when the circuit breaker is opened that increase the arc tension and give rise to arc instability that favors a decrease in the DC component and contributes to causing the current to pass through zero. That is the case described in French patent document No. 2 684 486.
Those solutions require novel devices to be used. The aim of the present invention is to solve the problem of interrupting fault currents having a delayed zero crossing while using conventional interrupting chambers only. The circuit breaker of the present invention requires no more than a particularly simple modification to the control apparatus.